$5B at $640/share is 7,812,500 shares, so if the selling pressure is from Tesla doing their cap raise, we should see that flush itself through the system fairly quickly given the volume.
I'd imagine it's spread out over at least 2, if not 3 or 4 days. They might also spread it out over stock price intervals, like $620, $640, $660, $680. Or 50% on the first day, then 25% on the second and third. There's a couple of possibilities, and there's no way to really know for sure. But the cap at $640 seems to still be in place even after that 20 minute macro dip, so $640 being the lower limit for the offering for today seems quite plausible.
They might prefer to get it done before the weekend, so that the new number of outstanding shares can be taken into consideration by the S&P.